AU2006202390A1 - Internal tie for a fluid storage tank - Google Patents

Description

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AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): BLUESCOPE STEEL LIMITED Invention Title: INTERNAL TIE FOR A FLUID STORAGE TANK The following statement is a full description of this invention, including the best method of performing it known to me/us: 2 INTERNAL TIE FOR A FLUID STORAGE TANK Technical Field The present invention relates generally to fluid storage tanks and more specifically to improvements in metal water tanks. The invention has been developed especially, but not exclusively, for rainwater storage tanks for domestic use and is herein described in that context. However, it is to be appreciated that the invention has broader application and is not limited to that particular use. For example, the tank may also be used in agriculture, aquaculture or viticulture.

Background of the Invention Traditionally, metal rainwater tanks have been made from corrugated metal panels which are formed with a circular cross section. The use of this cylindrical form is beneficial as it well suited to accommodate the hoop tension induced in the tank by the hydrostatic pressures of the water. Whilst the cylindrical water tanks are suited to resist the hydrostatic pressures, they are not particularly well suited for domestic applications because of aesthetic reasons and also because of space requirements.

In view of these limitations, in recent times, new designs of water tanks have been developed primarily for domestic use. The designs are generally of a rectangular cross section where the major front and back faces are significantly longer than side walls which interconnect the front and back faces. These designs are ideally suited to be located against building walls where they may be more easily accommodated and also where they will be less intrusive.

In the past, difficulties have been encountered in 61040 3 producing tanks, either in the original cylindrical form, or in the generally rectangular form, that are easy to manufacture and well suited to accommodate the hydrostatic pressures induced in the tank. Traditionally, prior art metal circular water tanks are assembled by hand thereby limiting the opportunity to reduce the cost of manufacture of such tanks. Plastic versions of these tanks are not self supporting and therefore require separate support and frames to be provided. These frames typically require extensive bridging which extend intermediate the tank and as such, the frames not only significantly increase the cost of manufacture of the tank, but can substantially reduce its storage capacity.

Summary of the Invention In a first aspect, the invention provides an internal tie for a fluid storage tank, the tie being an elongate member having opposite ends, opposite edges interconnecting said ends, and having a non linear cross section parallel to said ends.

In a particular form, the tie is formed from sheet material.

In a particular form, the opposite edges are spaced apart so that the tie is formed as an open section.

An advantage of making the tie from sheet material is that it can be shaped into various forms with different resultant characteristics, such as its strength and strain or creep characteristics. As such the tie can be better tailored to suit its intended application. In particular, the tie of this form can be specifically designed to be able to deform under threshold loading to inhibit excessive point loading at it's point of fixing with the tank wall, when that wall is bulging under internal hydrostatic forces.

A further advantage of using a sheet tie is that it enables linear fixing to the tank wall rather that point 61040 -4- C fixing in the case of a standard cable or bar. Also by providing some resilience in the sheet tie facilitates Cinstalling of the tie in a tank by allowing the tie to be compressed when locating it in position and then allowing it to expand when in position back to its natural state where it locates snugly within the tank.

In a particular form, the tie includes a plurality of fixing regions where the tie is arranged to be fixed to an A inner side of a wall of the tank, and at least one web C 10 that extends between respective ones of the fixing Sregions. In one form, the or each web extends generally in c-q a plane and the fixing regions are turned out of the plane of the or each web to which it joined. In this arrangement, the effective distance between the fixing regions can increase by opening up of the joint between respective ones of the webs and fixing regions.

In one form, the web is non-linear and the effective distance between fixing regions interconnected by the web can be increased by deformation of said web. In one form, the web has a generally corrugated profile.

In a particular embodiment, the tie comprises two end fixing regions and at least one intermediate fixing region, and a plurality of webs that interconnect pairs of said fixing regions. In this arrangement the tie is designed to be fixed to the tank wall in more than two positions.

In a particular form, the tie is formed from sheet metal. More particularly, the tie is formed from sheet steel that incorporates a corrosion resistant metal coating and a polymeric film overlay.

In yet a further aspect, the invention relates to a fluid storage tank having a tank wall extending about a central axis and having opposite ends spaced apart along the axis, and at least one tie according to any form described above disposed within the tank with its ends spaced apart in the direction of the tank axis, the tie being fixed to first and second portions of the tank wall 61040 5 that are angularly spaced apart about the tank axis.

In a particular form, the fluid storage tank includes a plurality of ties, one tie being spaced apart from an adjacent tie in the direction of the tank axis. In this way the ties are located one on top of the other and resemble baffles disposed in the tank.

In a particular form, a plurality of the ties are disposed one beside the other in the tank. In one form, there are a greater number of ties disposed at a lower end of the tank as compared to an upper end to cater for the greater hydrostatic pressure experienced at the lower end of the tank when it is full.

In a particular construction of tank, the tank wall is generally rectangular or obround and includes opposite side walls interconnecting opposite end walls, and wherein the or at least one of the ties interconnect the side walls.

The ties may be fixed to the tank wall in numerous different ways. For example, the tie may be connected to the wall by a clinching operation, by using mechanical fasteners or can be bonded to the tank wall by welding or by way of adhesive.

In yet a further aspect, the invention relates to a fluid storage tank having a tank wall extending about a central axis and having opposite ends spaced apart along the axis, and a plurality of stiffening members fixed to an inner side of the wall.

The stiffening members may be disposed at different orientations in the tank. For example, they could extend horizontally, vertically or diagonally, or a combination thereof.

In a particular form, the stiffening members are angularly spaced apart about the tank axis and each having opposite ends spaced apart in the direction of the tank axis.

In a particular embodiment, the stiffening members extend generally in the direction of the tank axis. In one 61040 6 form, the stiffening members are formed as channel sections.

The stiffening members provide rigidity to the tank wall. They may also form part of an internal tie to resist bulging of the tank wall. In this regard, in a particular form, the tank further comprising at least one tension element that extends between respective ones of the stiffening members.

In one form, the or each tension element is formed from a flexible material such as a cable or strap. In one form, the tension element is formed from steel such as stainless steel. In another form, the tension element may be formed from a polymeric material such as polyethylene.

In one embodiment, the tank includes a plurality of tension elements interconnecting respective ones of the stiffening members, the elements being spaced apart along the stiffening members. In a particular form, the spacings between adjacent elements are closer towards one lower end of the tank wall as compared to an opposite upper end.

In one form, the tank further comprising tension means operative to tension at least one of the tension elements extending between respective ones of the stiffening members.

In one form, the tank wall is formed from one or more lengths of sheet material. In a particular form, the sheet material is sheet metal and preferably sheet steel that incorporates a corrosion resistant metal coating and a polymeric film overlay.

The tank wall may be formed in a conventional manner where sheet metal strip is cut into sheets that are formed into cylinders by interconnecting the ends of respective sheets. The tank wall height is built up by placing subsequent sheets onto previous sheets that are formed to cylinders. Alternatively, the tank wall may be formed by a process of helically winding one or more sheets. In this latter arrangement, each sheet is helically wound about 61040 IND- 7 C the tank axis, and the wall further comprises at least one c-I seam extending helically about the tank axis that interconnects adjacent longitudinal edges of the or each sheet and forms a watertight joint along those edges.

In one form, the tank wall incorporates at least one stiffening formation. In a particular form, each stiffening formation includes at least one rib that extends helically about the tank axis.

In a particular form, the fluid storage tank is a (1 10 water storage tank.

IND

c- Brief Description of the Drawings It is convenient to hereinafter describe embodiments of the present invention with reference to the accompanying drawings. Particularly of these drawings and the related description is to be understood as not superseding the generality of the preceding broad description of the invention.

In the drawings: Fig. 1 is a perspective view of a water tank; Fig. 2 is a sectional view along section line II-II of the tank of Fig. 1; Fig. 3 is a sectional view along section line III-III of the tank of Fig. 2; Fig. 4 is a detailed view of a connection between a tie and tank wall; Fig. 5 is a variation in the profile of the tie used in the tank of Fig. 1; Fig. 6 is a further variation in the profile of the tie used in the tank of Fig. 1; Fig. 7 is a cross-sectional plan view of a second embodiment of the water tank; Fig. 8 is a cross-sectional elevation of the tank of Fig. 7; Fig. 9 is a cross-sectional elevation of the tank of Fig. 1 using the tie of Fig. 6; 61040 ID- 8 C Fig. 10 is a cross-section along section line X-X of the tank of Fig. 9; Fig. 11 is a cross-section along section line XI-XI of the tank of Fig. 9; and Fig. 12 is a cross-section along section line XII-XII of the tank of Fig. 9.

'qN Detailed Description of the Drawings (Ni

IND

Turning firstly to Figs. 1 and 2, a rainwater storage e tank 10 is disclosed which is generally obround in cross section. The tank includes a base 11 and tank wall 12 which extends upwardly from the base. The tank wall 12 includes opposite generally parallel sides 13 and 14 and generally semi-circular ends 15 and 16.

The tank 10 is made from sheet metal, with the tank wall 12 being formed by a single length of metal sheet 17, which is helically wound around a central axis (CA) of the tank. To ensure that the tank wall 12 is continuous, a lock seam 20 is provided which interconnects the opposing longitudinal edges 18, 19 of the sheet metal strip 17 that locate adjacent one another when the strip 17 is wound in a helix. The lock seam 20 similarly extends helically about the tank axis CA.

The sheet metal strip 17 may be profiled to include a plurality of ribs 21 which extend in the longitudinal direction of the sheet metal strip 17. In the illustrated form of Fig. 1, the sheet metal strip is profiled to include three ribs 21 which are in close proximity to each other and pans 22 located adjacent the ribs 21.

The ribs 21 are provided to stiffen the sheet strip 17 so that it is better able to accommodate the hydrostatic pressures induced in use of the tank These ribs are typically formed from a cold roll forming operation. Tanks that of that are formed using a helically winding process is the subject of a co-pending 61040 9 application WO 2005/005738 filed by the applicant, and the contents are herein incorporated by cross reference. It is to be appreciated however that the tank may be formed using other manufacturing processes and using other profiles and materials as will be appreciated by those skilled in the art.

Turning back to the form as illustrated in Fig. 1, the sheet 17 is helically wound so that the pitch angle a as illustrated in Fig. 1 is relatively low and is typically in the range of 0.1 to 50. Further, in the illustrated form, the ribs 21 project outwardly from the tank. However it is to be appreciated that the tank may be wound so that the ribs extend inwardly.. This latter option has the advantage as it provides a smoother exterior surface with the outer surface of the pans 22 forming the outer margins of the tank wall 12.

The sheet metal strip 17 is formed from a high tension or mild steel which typically has thickness of 0.35 3.0mm and incorporates a protective coating which is formed from zinc or a zinc mixture. The sheet steel may also be laminated with a protective polymer based film which provides superior chemical resistance and enhanced moisture barrier. One such polymer film is sold under the trade mark TRENCHCOAT LG which is a trade mark of the Dow Chemical Company. The thickness of the coating is preferably in the range of 100 to 400 microns.

Whilst not shown, the tank 10 typically also includes a lid which incorporates an inlet pipe to the tank 10. An outlet (also not shown) is also typically provided adjacent the base 11.

Figs. 2 and 3 illustrate internal ties (generally designated 23) which are connected to the tank wall 12 so that it can accommodate the hydrostatic pressures induced in the tank in use. The ties 23 are arranged to interconnect portions of the tank wall 12 so as to resist outward bowing of the tank wall 12 under those hydrostatic pressures. In use, a plurality of the ties may be 61040 10 disposed within the tank 10 between its upper and lower ends. The spacings between the ties 23 may vary along the tank and in particular, be more closely spaced towards the bottom of the tank 10 where the hydrostatic pressures are at their highest.

In the form as shown in Figs 2 and 3, the ties 23 are formed from sheet material 24 that is profiled into a nonlinear shape, which in the illustrated form is a Zsection. In this way the ties include a web portion interconnecting opposite flanges 26. The flanges provide the fixing regions where a respective tie 23 is connected to the tank wall 12. The tie can be secured to the tank wall by any suitable means such as through a clinching operation or by the use of mechanical fasteners.

Alternatively the ties may be secured in place using a welding process or through the use of an adhesive.

Fig. 4 illustrates a fixing of the tie to a tank wall where the tank wall is corrugated. In that arrangement, the tie flange 26 is profiled to include a similar corrugated profile and a gasket 27 is disposed between the tie flange 26 and the tank wall 12. Mechanical fasteners 28 are used to fix the tie and gasket 27 to the tank wall 12.

As indicated above, the ties 23 are formed from sheet metal and may of a similar structure as the tank wall. In this way, the sheet metal strip 24 is formed from a high tension or mild steel which typically has thickness of 0.35 3.0mm and incorporates a protective coating such as the polymer film sold under the trade mark TRENCHCOAT LG.

Fig. 3 illustrates a typical set out of the sheet metal ties 23 in the tank 10. As the hydrostatic pressures are higher in the lower section of the tank, the tank includes a series of four closely spaced sheet ties (23a, 23b, 23c and 23d) located side by side. These ties only extend part way up the tank wall and located above those ties are three further ties (23e, 23f and 23g). In turn located on top of those three ties is a single tie 61040 11 23h. The layout of these ties caters for the different strength requirements at the different depths in the tank due to the increase in hydrostatic pressure on increasing depth of water in the tank. It is to be appreciated that the exact configuration could vary depending on the structure of the tank and/or the tie including its shape and wall thickness. The applicant has found that for the obround tanks of Fig. 1 a spacing of about 400mm is required between the ties at the bottom of the tank.

Figs. 5 and 6 illustrate variations in the profile of the tie 23. In the arrangement of Fig. 5, the sheet strip is profiled in a C-section, whereas Fig. 6 illustrates a more complex arrangement where the tie has a generally Wsection. With the arrangement of Figs 6, the tie includes two webs 25 and three flanges 26, thereby providing three fixing regions to the tank wall 12.

Figs. 7 and 8 illustrate alternative arrangement of ties. Rather than using sheet material, the tie 30 is formed from stiffening members 31 that are mounted to the internal side of the tank wall 12 and tension elements 32 that interconnect those stiffening members. These stiffening members are formed in the illustrated form from channel section and provide rigidity to the tank wall. In another form, the stiffening members may be formed from a box section. The stiffening members may be fixed to the wall using any suitable mechanical fastening arrangement or by a welding process or through the use of an adhesive.

The tension elements 32 extend between pairs of respective stiffening members. These tension elements may be connected through apertures formed in the stiffening members, or could loop around the tension elements.

Further, the tension elements could extend between more than two stiffening members.

In the illustrated form, the elements 32 comprise stainless steel cables which are tensioned by the use of turnbuckles 33. In another form, the tension elements 61040 12 could be formed from a polymeric material such as polyethylene. Further as the hydrostatic pressure is higher than the lower parts of the tank, the spacing between the cables is reduced towards the lower end of the tank The use of the stiffening members 31 provide rigidity to the tank wall and accordingly improve the structural performance of the tank 10, even if the cables (or other tension elements) are not used. When used as part of a tie, the stiffening members have the added advantages of allowing a convenient anchor point for the tension elements and reducing point loading on the tank wall as the stiffening member allow the loading from the elements to be better distributed across that member.

Figs. 9 to 12 illustrate a typically set out of the sheet metal ties 23 in a tank 10 using the tie of Fig. 6.

As the hydrostatic pressures are higher in the lower section of the tank, the tank includes a series of three closely spaced sheet ties (23a, 23b, 23c) located side by side. These ties only extend part way up the tank wall and located above those ties are two further ties (23d, 23e) and, located on top of the pair of ties is a single tie 23f. In this way, the layout of the ties reflects the need for different strength at different depths in the tank In accordance with the present invention, an improved water tank and internal tie arrangement is disclosed. The ties can be fitted to the tank post forming and allow for variation in the strength at different depth levels. Also the ties reduce point loading at the tie fixing points on the tank wall. This is achieved in one form by having a tie formed from profiled sheet that provides the capacity to flex through deformation of the section which is not possible in a linear section. In another form, the ties are connected to stiffening members thereby allowing the distribution of load from the ties across those members.

61040 13 In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprising" is used in an inclusive sense, i.e. the features specified may be associated with further features in various embodiments of the invention.

Variations and or modifications may be made to the parts previously described without departing from the spirit or ambient of the present invention.

61040

Claims (25)

1. An internal tie for a fluid storage tank, the tie being an elongate member having opposite ends, opposite spaced apart edges interconnecting said ends, and having a non linear cross section parallel to said ends.

2. A tie according to claim 1, wherein the tie is formed from sheet material.

3. A tie according to claim 1 or 2, wherein the edges 1D 0 are spaced apart so that said tie forms an open section.

4. A tie according to any preceding claim, wherein each tie includes a plurality of fixing regions where the tie is arranged to be fixed to an inner side of a wall of the tank, and at least one web that extends between respective ones of the fixing regions. A tie according to claim 4, wherein the or each web extends generally in a plane and the fixing regions are turned out of the plane of the or each web to which it joined, wherein the effective distance between the fixing regions can increase by opening up of at least one of the joints between said web and said fixing region.

6. A tie according to claim 4, wherein the web is non- linear and wherein the effective distance between fixing regions interconnected by said web can be increased by deformation of said web.

7. A tie according to claim 6, wherein said web has a generally corrugated profile.

8. A tie according to any one of claims 4 to 7, comprising two end fixing regions and at least one intermediate fixing region, and a plurality of webs that interconnect pairs of said fixing regions.

9. A tie according to any preceding claim, wherein the tie is formed from sheet metal. 61040 D 15 A tie according to claim 9, wherein the tie is formed from sheet steel that incorporates a corrosion resistant metal coating and a polymeric film overlay.

11. A fluid storage tank having a tank wall extending M 5 about a central axis and having opposite ends spaced apart along said axis, and at least one tie according to any h preceding claim disposed within said tank with its ends spaced apart in the direction of the tank axis, the tie q being fixed to first and second portions of said tank wall IND that are angularly spaced apart about said tank axis. c- 12. A fluid storage tank according to claim 11, wherein said tank includes a plurality of said ties, one tie being spaced apart from an adjacent tie in the direction of said tank axis.

13. A fluid storage tank according to either claim 11 or 12, wherein a plurality of said ties are disposed one beside the other in said tank.

14. A fluid storage tank according to any one of claims 11 to 13, wherein said tank wall is generally rectangular or obround and includes opposite side walls interconnecting opposite end walls, and wherein the or at least one of the ties interconnect said side walls. A fluid storage tank according to any one of claims 11 to 14, wherein the or each tie is fixed to said tank wall by mechanical fasteners.

16. A fluid storage tank having a tank wall extending about a central axis and having opposite ends spaced apart along said axis, and a plurality of stiffening members fixed to an inner side of said wall.

17. A fluid storage tank according to claim 16, wherein said stiffening members are angularly spaced apart about said tank axis and each have opposite ends spaced apart in the direction of the tank axis. 61040 ND 16

18. A fluid storage tank according to claim 17, wherein said stiffening members extend generally in the direction Sof said tank axis.

19. A fluid storage tank according to any one of claims 16 to 18, wherein said stiffening members are formed as channel sections.

20. A fluid storage tank according to any one of claims e 16 to 20, wherein the stiffening members form part of at e least one internal tie for said tank to resist outward IND bulging of said tank wall, said tie further comprising at cq least one tension element that extends between respective ones of the stiffening members.

21. A fluid storage tank according to claim 20, wherein the or each tension element is formed from a flexible material such as a cable or strap.

22. A fluid storage tank according to claims 20 or 21, wherein the tank includes a plurality of tension elements interconnecting respective ones of the stiffening members, the tension elements being spaced apart along the stiffening members.

23. A fluid storage tank according to claim 22, wherein the spacings between adjacent tension elements are closer towards one lower end of the tank wall as compared to an opposite upper end.

24. A fluid storage tank according to any one of claims to 23, further comprising tension means operative to tension at least one of the tension elements extending between respective ones of the stiffening members. A fluid storage tank according to any one of claims 11 to 24, wherein the tank wall is formed from one or more lengths of sheet material.

26. A fluid storage tank according to claim 25, wherein the sheet material is sheet metal. 61040 17

27. A fluid storage tank according to claim 26, wherein the sheet material is sheet steel that incorporates a corrosion resistant metal coating and a polymeric film overlay.

28. A fluid storage tank according to any one of claims to 27, wherein each sheet is helically wound about the tank axis, and the wall further comprising at least one seam extending helically about the tank axis that interconnects adjacent longitudinal edges of the or each sheet and forms a watertight joint along those edges.

29. A fluid storage tank according to claim 28, wherein the tank wall incorporates at least one stiffening formation. A fluid storage tank according to claim 29, wherein each stiffening formation includes at least one rib that extends helically about the tank axis.

31. A fluid storage tank according to any one of claims 11 to 30, wherein the tank is a water storage tank. Dated this 30th day of May 2006 BLUESCOPE STEEL LIMITED By their Patent Attorneys GRIFFITH HACK 61040